Chucker partridge trying to mate with my chickens

we have a flock of 10 chickens and a chucker partridge flew in our yard last year and has become one of the flock. We have a rooster but they still get along well. The chucker is a male, and recently he’s been climbing on my hens and mating with them. I’m not sure what to do or if there could be a mixed breed of chickens and chucker? Anyone heard of this??